i didnt see this thread until now, but i can comment from what i heard 3rd person
the reason why bedatz is more expensive is because by rubin and landau they have 3 bins, one for kosher, one for treif and one for safek. the treif bin is sold to the arabs and the safek bin is sold to the rabbanut.
since the bedatz doesnt do business with the rabbanut, both bins are sold to the arabs, thus commanding a lower price
i dont know this first hand though